Method of making grain-oriented laminations for magnetic core structures



July 29,1969

B. B. MICHIULIS OF MAKING MAGNETIC CORE STRUCTURES Filed April 28, 1967 METHOD DIRECTION OF GRAIN GRAIN-ORIENTED LAMINATIONS FOR DIRECTION OF GRAIN IO F|G.l

INVENTOR I BRUNOENICHULIS TTORNEY United States Patent METHOD OF MAKING GRAIN-ORIENTED LAMI- NATIONS FOR MAGNETIC CORE STRUCTURES Bruno B. Michiulis, Wood Dale, Ill., assignor to Sola Basic Industries, Inc., Milwaukee, Wis., a corporation of Wisconsin Filed Apr. 28, 1967, Ser. No. 634,720 Int. Cl. 1101f 3/04, 7/06 US. Cl. 29-609 9 Claims ABSTRACT OF THE DISCLOSURE A method of making stacked magnetic cores with a minimum of scrap, the cores having elongated E-shaped members and short E-shaped members.

This has resulted in waste of material in such a structure.

Furthermore, with the use of grain oriented magnetic material and the desirability of having the magnetic properties in the various elements of the core properly related to each other, such has been found difiicult to attain and has resulted in considerable waste of material. Commercial E-I structures have been utilized also for making these devices, but to achieve proper ratios of the various parts of the magnetic structure, modifications have been required which also result in waste of material.

In one aspect of the invention, a die arrangement is employed for operating on magnetic strip or sheet mate rial of the grain-oriented type. The die is formed so that two elongated E-shaped laminations or members having the open E facing each other and a pair of narrow or short E-shaped members, nestled between the legs of the two elongated E-shaped members, are stamped from the strip with the base of each elongated member extending across the grain and the bases of the short members extending with or along the grain. The width of the base portions of the E-shaped short members is substantially the same as the width of the outer legs of the elongated members, and the widths of the legs of the short members are the same as those of the elongated members.

In a preferred form the several portions of the E- shaped members have a definite proportional relationship or rat-i0 as will be described in detail hereafter.

The principal object of the invention is to form a core lamination for high leakage reactance transformers which will give the most efiicient operation with the most economical use of material.

In the drawings:

FIG. 1 shows an assembled core structure having the laminations grain oriented as indicated by arrows; and

FIG. 2 shows the manner of arranging the dies for the substantially scrapless stamping of the laminations for the core of FIG. 1.

The present core structure is particularly useful in conjunction with a high leakage reactance transformer such as illustrated in the aforesaid U.S. Patent No. 2,143,745. It also is especially adapted for forming high leakage reactance transformers such as disclosed in Patent No. 2,806,199. Referring to FIG. 2, the die arrangement is such as to provide a pair of elongated E-shaped laminations or members 10 each having outer legs 11 and 12 and a center leg 13. As indicated by the arrows, the legs 11, 12 and 13 lie along or in the direction of the grain while the base portion 14 lies across the grain of the grain-oriented strip 15. A pair of narrow or short E- shaped members 16 are nestled between the legs of the two elongated E-shaped members and have their bases extending along the grain of strip 15. The dies are also arranged to provide cutouts 17 to form the short outer legs 18 and center legs 19 of the narrow E members. Thus, the only scrap involved are the pieces 17 to form the short legs of the narrow E-shaped members. The amount of scrap involved, for example, is as low as 3%.

The assembled core structure in shown in FIG. 1 and is formed by stacking a plurality of the stampings or laminations 10 and 16 on top of each other with the short E members 16 abutting against the appropriate ends of the legs of the elongated E members 10. The aligned and stacked stampings are held together by welding down the seams 20 on each side thereof. It will be noted that two pairs of stampings 10 and 16 are formed by each stamping operation. Thus two layers of the stacked laminations are provided by each such operation. It is also to be noted that the joint 21 between the center legs 13 and 19 will fall within the coil wound on the center leg of the core structure whereby the coil will securely hold the center leg portions together and reduce the audible noise that otherwise might exist if the leg portions were loosely butted such as if an I piece was butted across the open end of the elongated E. 7

Magnetic shunts 22 can be formed from metal and placed in position as illustrated, as is well known in the art.

As above stated, a further aspect of the invention is the proper proportioning of the several parts of the core structure to obtain maximum magnetic proportions. For example, in the device of FIG. 1, the center legs 13 and 19 can be considered to be made equal to one unit. The outer legs 12 and 18 can then be between .6 to .7 unit. The window widths or distance between the center and outer legs can be made between .8 and .9. The width of the base of the narrow E member should be made approximately the same as the width of the outer legs of the E-shaped members, i.e., between .6 to .7 unit. The length of the bases of the E-shaped members should be approximately twice the length of the legs of the elongated member. In view of the difference in magnetic properties of cross-grain and width-grain, it is necessary to make the width of the base 14 of the elongated E-shaped piece, which is cross-grain, wider than the base of the short E-shaped member 16. As an example, this should be made so that the base 14 of elongated E member 10 is .8 to .9 unit.

The above ratios have been found to be desirable to obtain the optimum performance of the device and at the same time to be able to produce laminations with substantially no scrap except that as indicated. It should also be apparent that the principles described above could be used in conjunction with other high leakage reactance transformers such as that of US. Patent No. 2,694,177, and it is intended that the invention be limited only by the scope of the appended claims.

What is claimed is:

1. The method for the substantially scrapless production of grain-oriented laminations for a high leakage reactance transformer core or the like which comp-rises stamping two elongated opposed E-shaped members from a sheet of grain-oriented magnetic material with the base of each member extending across the grain and the legs of the members extending along the grain, and simultaneously stamping a pair of short E-shaped members from said sheet of grain-oriented material, said short members being nestled between the legs of said elongated members with their bases extending in the direction of said grain and having a width substantially the same as the width of the outer legs of the elongated members.

2. The method defined in claim 1 wherein the base of said elongated E-shaped members has a width substantially greater than the outer legs of the elongated memher.

3. The method as defined in claim 1 wherein the center legs of said E-shaped members have a relative width of 1 unit and the outer legs of said member have a width in the range of .6 to .7 unit.

4. The method as defined in claim 3 wherein the base of said short E-shaped members has a width in the range of .6 to .7 unit.

5. The method as defined in claim 4 wherein the base of said elongated E-shaped member has a width in the range of .8 to .9 unit.

6. The method as defined in claim 5 wherein the distance between the center and outer legs is in the range of .8 to .9 unit to provide windows of such width in an assembled core structure.

7. The method as defined in claim 2 wherein the length of the bases of said E-shaped members is approximately twice the length of the legs of the elongated members.

8. The method as defined in claim 6 wherein the length of the bases of said E-shaped members is approximately twice the length of the legs of the elongated members.

9. The method for forming a grain-oriented laminated magnetic core structure for high leakage reactance transformers or the like which comprises stamping two elongated opposed E-shaped members from a sheet of grainoriented magnetic material with the base of each member extending across the grain and the legs of the members extending along the grain, and simultaneously stamping a pair of short E-shaped members from said sheet of grain-oriented material, said short members being nestled between the legs of said elongated members with their bases extending in the direction of said grain and having a width substantially the same as the width of the outer legs of the elongated members, the base of the elongated E-shaped members having a width substantially greater than the outer legs of the elongated member, stacking a plurality of said E-shaped members with the legs of the short members forming butt joints with the legs of the elongated members, and welding the stacked members along said butt joints of the outer legs.

References Cited UNITED STATES PATENTS 509,770 11/1893 Scott 29609 X 1,877,254 9/1932 Ritter 29609 X 2,934,727 4/ 1960 Cornell 336212 JOHN F. CAMPBELL, Primary Examiner C. E. HALL, Assistant Examiner U.S. Cl. X.R. 83-32; 3362l2 

